Aeolian processes across transverse dunes. II: Modelling the sediment transport and profile development

This paper discusses a model which simulates dune development resulting fro m aeolian saltation transport. The model was developed for application to c oastal foredunes, but is also applicable to sandy deserts with transverse d unes. Sediment transport is calculated using published deterministic and em pirical relationships, describing the influence of meteorological condition s, topography, sediment characteristics and vegetation. A so-called adaptat ion length is incorporated to calculate the development of transport equili brium along the profile. Changes in topography are derived from the predict ed transport, using the continuity equation. Vegetation height is incorpora ted in the model as a dynamic variable. Vegetation can be buried during tra nsport events, which results in important changes in the sediment transport rates. The sediment transport model is dynamically linked to a second-orde r closure air flow model, which predicts friction velocities over the profi le, influenced by topography and surface roughness. Modelling results are shown for (a) the growth and migration of bare, initi ally sine-shaped dunes, and (b) dune building on a partly vegetated and ini tially flat surface. Results show that the bare symmetrical dunes change in to asymmetric shapes with a slipface on the lee side. This result could onl y be achieved in combination with the second-order closure model for the ca lculation of air flow. The simulations with the partly vegetated surfaces r eveal that the resulting dune morphology strongly depends on the value of t he adaptation length parameter and on the vegetation height. The latter res ult implies that the dynamical interaction between aeolian activity and veg etation (reaction to burial, growth rates) is highly relevant in dune geomo rphology and deserves much attention in future studies. Copyright (C) 1999 John Wiley & Sons Ltd.